Catalyst carrier for autothermal reforming processes

ABSTRACT

Methods for autothermal reforming with a red mud catalyst support composition, one method including providing a methane feed with oxygen and carbon dioxide to react over the red mud catalyst support composition at increased temperature and increased pressure to produce synthesis gas comprising H2 and CO, the composition comprising red mud material produced from an alumina extraction process from bauxite ore.

BACKGROUND Field

Embodiments of the disclosure relate to catalyst carrier compositions for use in reforming processes. In particular, certain embodiments of the disclosure relate to catalyst carrier compositions for and methods of autothermal reforming.

Description of the Related Art

Autothermal reforming of methane energetically combines endothermic dry reforming and exothermic partial oxidation of methane, and this provides advantages to autothermal reforming technology for hydrogen production. In autothermal reforming, methane, CO₂ and O₂ are used to produce carbon monoxide and hydrogen (syngas) as shown below in Equation 1. 2CH₄+CO₂+O₂⇄3H₂+3CO+H₂O  Eq. 1

One challenge of methane reforming is quick deactivation due to coke formation on the surface of catalysts. In addition, high temperatures for methane conversion can lead to catalyst deactivation by coking or sintering. Nickel catalyst with aluminum oxide and magnesium oxide as supports is used for methane reforming.

Autothermal reforming technology combines dry reforming technology and partial oxidation of methane technology to produce hydrogen in such a manner that the global process is almost thermally neutral or slightly exothermic, thus achieving efficiencies for heat exchange and an operating temperature control framework that reduces hot spot formation to prevent catalyst deactivation by sintering or coking.

However, present catalyst technology is insufficient in some processes to provide cost-effective and durable means for autothermal reforming.

SUMMARY

Applicant has recognized a need for catalyst carrier compositions comprising red mud to be applied in systems and processes for autothermal reforming. Red mud catalyst carrier compositions for use in autothermal reforming are disclosed. The red mud catalyst carrier compositions in some embodiments contain Fe, Al, Si, Na, Ca, and Ti oxides from red mud, and the compositions act as a base support for catalytically active compositions, for example added metals and metal oxides. A factor in designing suitable reforming catalysts is the catalyst support or base material, which can have an active catalytic role in a catalytic reaction or be merely inert. In embodiments of the present disclosure, red mud acts as a catalyst carrier. Disclosed compositions are useful as a catalyst carrier in autothermal reforming processes for the conversion of methane to syngas, according to Equation 1. Utilization of red mud in autothermal reforming processes provides the concurrent advantages of utilizing a waste material (red mud), converting CO₂ (a greenhouse gas), and producing H₂.

Red mud is a caustic waste material produced from bauxite ore processing for alumina extraction, and is utilized here as a catalyst carrier for an autothermal reforming process. Surprisingly and unexpectedly, without being specifically designed as a catalyst or carrier (for example using specific zeolitic structure), red mud waste material can be readily used as a catalyst carrier. Autothermal reforming is considered to be a green method for the production of syngas (H₂ and CO), since it utilizes as reactants two greenhouse gases, CH₄ and CO₂. Red mud generally includes a mixture of transition metals such as Ti, Fe, and Al, which make it an advantageous catalyst in addition to or alternative to catalyst carrier for autothermal reforming processes, for example once modified with nickel in addition to or alternative to other metals, such as transition metals and their oxides.

Embodiments disclosed here apply red mud as a catalyst support or base material, while offering some catalytic activity itself for autothermal reforming of methane.

Therefore, disclosed here is a method for autothermal reforming with a red mud catalyst support composition, the method including providing a methane feed with oxygen and carbon dioxide to react over the red mud catalyst support composition at increased temperature and increased pressure to produce synthesis gas comprising H₂ and CO, the composition comprising: red mud material produced from an alumina extraction process from bauxite ore. In some embodiments, the composition further comprises at least one added catalytic metal, the added catalytic metal not being present in an unmodified form of the red mud material produced from the alumina extraction process from bauxite ore. Still in other embodiments, the at least one added catalytic metal is a Periodic Table Group 3-12 metal. In certain embodiments, the increased temperature is between about 500° C. to about 1000° C. In other embodiments, the increased temperature is between about 600° C. to about 800° C. In yet other embodiments, the increased temperature is between about 700° C. to about 750° C.

In other embodiments of the method, the increased pressure is between about 5 bar and about 20 bar. Still in certain other embodiments, the increased pressure is between about 7 bar and about 15 bar. In some embodiments, the increased pressure is about 14 bar. Still in other embodiments, gas hourly space velocity of the methane feed and carbon dioxide feed mixed is between about 1000 h⁻¹ to 10000 h⁻¹, or is about 3,000 h⁻¹ or is about 5000 h⁻¹. In some embodiments, the composition includes at least one component selected from the group consisting of: Fe₂O₃, Al₂O₃, SiO₂, Na₂O, CaO, and TiO₂. Still in other embodiments, a majority of the particles of the composition have a particle size of less than about 70 μm.

In still other embodiments, a molar ratio is about 2:1:1 for CH₄:CO₂:O₂. In some embodiments, produced H₂ is at least about 10 mol. % of produced products from the reaction for at least about 6 hours. In certain embodiments, the composition includes between about 20 wt. % and about 30 wt. % Al₂O₃, between about 5 wt. % and about 10 wt. % CaO, between about 15 wt. % and about 25 wt. % Fe₂O₃, between about 5 wt. % and about 15 wt. % Na₂O, between about 15 wt. % and about 25 wt. % SiO₂, and between about 5 wt. % and about 10 wt. % TiO₂.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present disclosure will become better understood with regard to the following descriptions, claims, and accompanying drawing. It is to be noted, however, that the drawing illustrates only several embodiments of the disclosure and are therefore not to be considered limiting of the disclosure's scope as it can admit to other equally effective embodiments.

FIG. 1 is a graph showing mol. % of H₂ out of the total products produced from autothermal reforming of CH₄ in an autothermal reforming process for unmodified red mud used as a catalyst support (RM) and for MgO used as a catalyst support.

DETAILED DESCRIPTION

So that the manner in which the features and advantages of the embodiments of compositions of red mud along with systems and methods for autothermal reforming with such compositions, may be understood in more detail, a more particular description of the embodiments of the present disclosure briefly summarized previously may be had by reference to the embodiments thereof, which are illustrated in the appended drawing, which forms a part of this specification. It is to be noted, however, that the drawing illustrates only various embodiments of the disclosure and are therefore not to be considered limiting of the present disclosure's scope, as it may include other effective embodiments as well.

As noted, red mud is a caustic waste material generated during alumina extraction from bauxite ore. Red mud includes a mixture of transition metals, for example as listed in Table 1.

TABLE 1 Example composition ranges for global red mud. Component Fe₂O₃ Al₂O₃ SiO₂ Na₂O CaO TiO₂ Approx. 30-60% 10-20% 3-50% 2-10% 2-8% 10% Weight Percentage

In one embodiment, a Saudi Arabian red mud sample was evaluated for autothermal reforming activities at 750° C. and 14 bar, as shown in FIG. 1. The results are compared to MgO catalyst support material. MgO is a commercially-available catalyst support material known for a variety of reforming processes with a surface area of about 29 m²/g. The MgO was tested as received. FIG. 1 shows that red mud surprisingly and unexpectedly outperforms MgO as a support for autothermal reforming catalyst in terms of hydrogen production (also methane conversion according to Equation 1), especially at high pressure which is a preferred condition for industry application of autothermal reforming.

Saudi Arabian red mud from Ma'aden Aluminium Company, based at Ras Al Khair, Saudi Arabia was used in the test runs. Table 2 shows the weight percent for certain components in the Saudi Arabian red mud composition.

TABLE 2 Certain component weight percentages in Saudi Arabian red mud (RM) catalyst/catalyst support composition. Component Fe₂O₃ Al₂O₃ SiO₂ Na₂O CaO TiO₂ Weight 18.75% 25.22% 18.88% 11.77% 7.97% 6.89% Percentage

The red mud was tested as-is without further treatment, for example acid or base treatment, for use as a catalyst support with a Brunauer-Emmett-Teller (BET) surface area of about 16 m²/g.

Several tests on red mud support catalytic activity and MgO support catalytic activity for autothermal reforming were experimentally conducted. Saudi Arabian red mud was tested as received as a catalyst support without any modifications, and it was placed in a Micromeritics® PID Eng & Tech brand microactivity reactor designed for catalyst activity and selectivity analysis, and similar tests were performed for the MgO catalyst support. The results are compared, for example, in FIG. 1. Results show that red mud catalyst support catalytic activity for autothermal reforming is advantageously improved over MgO catalyst support catalytic activity for autothermal reforming.

FIG. 1 is a graph showing mol. % of H₂ out of the total products produced from autothermal reforming of CH₄ in an autothermal reforming process for unmodified red mud used as a catalyst support and for MgO used as a catalyst support. Experimental conditions in the autothermal reforming reactor included temperature at about 750° C. and pressure at about 14 bar. In some embodiments, gas hourly space velocity (GHSV) of the mixed feed is between about 1000 h⁻¹ and 10000 h⁻¹, or GHSV can be between about 3000 h⁻¹ to about 6000 h⁻¹, or about 3517 h⁻¹. The test was conducted for 7 hours. In some embodiments, the feed was about 50 mol. % methane, 25 mol. % CO₂, and 25 mol. % O₂ for both catalyst supports tested. The GHSV was calculated for the mixed feed. For autothermal reforming, the feed composition can comprise, consist of, or consist essentially of CH₄, CO₂, and O₂. Based in part on thermodynamics, the molar ratio can be about 2:1:1 for CH₄:CO₂:O₂. GHSV generally measures the flow rate of the feed gases divided by the catalyst volume, which indicates the residence time of the reactants on the catalyst.

FIG. 1 shows mol. % of H₂ out of the total products produced from autothermal reforming of CH₄ in an autothermal reforming process for unmodified red mud used as a catalyst support and for MgO used as a catalyst support. Hydrogen production illustrated in FIG. 1 shows that untreated red mud produced hydrogen between about 16 mol. % and about 10 mol. % up to 7 hours, whereas MgO catalyst support produced only between about 9.0 mol. % to about 1.0 mol. % hydrogen.

The singular forms “a,” “an,” and “the” include plural referents, unless the context clearly dictates otherwise. The term “about” when used with respect to a value or range refers to values including plus and minus 5% of the given value or range.

In the drawings and specification, there have been disclosed example embodiments of the present disclosure, and although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. The embodiments of the present disclosure have been described in considerable detail with specific reference to these illustrated embodiments. It will be apparent, however, that various modifications and changes can be made within the spirit and scope of the disclosure as described in the foregoing specification, and such modifications and changes are to be considered equivalents and part of this disclosure. 

What is claimed is:
 1. A method for autothermal reforming with a red mud catalyst support composition, the method comprising the steps of: providing a methane feed with oxygen and carbon dioxide to react in an autothermal reforming reaction over the red mud catalyst support composition at a temperature between about 500° C. to about 1000° C. and a pressure between about 5 bar and about 20 bar to produce synthesis gas comprising H₂ and CO, the red mud catalyst support composition comprising: red mud waste material produced from an alumina extraction process from bauxite ore with a weight ratio of aluminum oxide to iron oxide of about 1:0.74 and a weight ratio of aluminum oxide to titanium oxide of about 1:0.27, where produced H₂ is at least about 10 mol. % of produced products from autothermal reforming for at least about 6 hours.
 2. The method according to claim 1, where the red mud catalyst support composition further comprises at least one added catalytic metal, the added catalytic metal not originally being present at greater than about 1 wt. % in the red mud waste material produced from the alumina extraction process from bauxite ore.
 3. The method according to claim 2, where the at least one added catalytic metal is a Periodic Table Group 3-12 metal.
 4. The method according to claim 1, where the increased temperature is between about 600° C. to about 800° C.
 5. The method according to claim 1, where the increased temperature is about 750° C.
 6. The method according to claim 1, where the increased pressure is between about 10 bar and about 15 bar.
 7. The method according to claim 1, where the increased pressure is about 14 bar.
 8. The method according to claim 1, where gas hourly space velocity of the methane feed with oxygen and carbon dioxide is between about 1000 h⁻¹ to 10000 h⁻¹.
 9. The method according to claim 1, where the red mud catalyst support composition includes at least one component selected from the group consisting of: Fe₂O₃, Al₂O₃, SiO₂, Na₂O, CaO, and TiO₂.
 10. The method according to claim 1, where a majority of particles of the red mud catalyst support composition have a particle size of less than about 70 μm.
 11. The method according to claim 1, where a molar ratio is about 2:1:1 for CH₄:CO₂:O₂.
 12. The method according to claim 1, where the red mud catalyst support composition includes between about 5 wt. % and about 10 wt. % CaO, between about 5 wt. % and about 15 wt. % Na₂O and between about 15 wt. % and about 25 wt. % SiO₂. 